Silicon nitride films and methods

ABSTRACT

Described are methods of making SiN materials on substrates, particularly SiN thin films on semiconductor substrates. Improved SiN films made by the methods are also included.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit under 35 USC §119(e) of U.S.provisional patent application No. 61/324,710, filed Apr. 15, 2010, andU.S. provisional patent application No. 61/372,367, filed Aug. 10, 2010,and U.S. provisional patent application No. 61/379,081, filed Sep. 1,2010, and U.S. provisional patent application No. 61/417,807, filed Nov.29, 2010, each of which is incorporated herein by reference in itsentirety and for all purposes. This application is related to U.S.patent application Ser. No. ______ [Attorney docket No. NOVLP405], andU.S. patent application Ser. No. ______ [Attorney docket No.NVLS003674], each filed on the same day as the instant disclosure andeach incorporated herein by reference in its entirety and for allpurposes.

INTRODUCTION

1. Field

The present disclosure relates generally to formation of SiN materialson substrates. More particularly, the disclosure relates to formation ofSiN films on semiconductor substrates.

2. Background

Silicon nitride (SiN) thin films have unique physical, chemical andmechanical properties and thus are used in a variety of applications,particularly semiconductor devices, for example in diffusion barriers,gate insulators, sidewall spacers, encapsulation layers, strained filmsin transistors, and the like. One issue with SiN films is the relativelyhigh temperatures used to form the films, for example, in Front End ofLine (FEOL) applications, SiN films are typically deposited by chemicalvapor deposition (CVD) in a reactor at greater than 750° C. usingdichlorosilane and ammonia. However, as SiN films are used in late-stagesemiconductor fabrication processes, and as device dimensions continueto shrink, there is an increasing demand for SiN films to be formed atlower temperatures, for example less than 600° C.

Another issue with SiN film depositions is the occurrence and/or buildupof amine salts in the reaction chamber. These salts are formed byreaction of amine reactants and acid by products, for example, hydrogenchloride and amine reactants combining It would be useful to havemethods which reduce the amount of salts formed and thus improveprocessing by, for example, reducing downtime needed to clean reactorsand improving film quality.

Another issue with SiN films is, in certain instances, unwanted carboncontent in the film due to carbon content of reactants used to form theSiN film. One way that such carbon content is removed is by hightemperature anneal, for example, greater than 600° C., and thus theaforementioned finer features are jeopardized. Of course there areinstances where carbon content is desirable, and it would be helpful ifone could more precisely tailor the carbon content of the film.

A useful way to deposit SiN films is atomic layer deposition (ALD) andvariants thereof, for example, plasma enhanced ALD (PEALD). Under ALDprocesses, the reaction chamber is purged after every reactant isintroduced for adsorption onto the substrate surface. It would behelpful to have processes where one or more purges were unnecessary andthus, for example, throughput would be increased.

What is need are improved SiN films and methods of making them.

SUMMARY

Described are methods of making SiN materials on substrates,particularly SiN thin films on semiconductor substrates. Improved SiNfilms made by the methods are also included.

One embodiment is a method of forming a silicon nitride material on asubstrate, including: (a) providing the substrate in a reaction chamber;(b) continuously exposing the substrate to a vapor phase flow of anitrogen-containing reactant wherein the nitrogen-containing reactant isadsorbed onto the surface of the substrate; (c) periodically exposingthe substrate to a vapor phase flow of a silicon-containing reactantwherein the silicon-containing reactant is adsorbed onto the surface ofthe substrate; and (d) periodically igniting a plasma in the reactionchamber when the vapor phase flow of the silicon-containing reactant hasceased. In this embodiment, the plasma is ignited to form a plasma fromthe nitrogen-containing reactant flowing in the reaction chamber. In oneembodiment, a carrier gas is flowed continuously through the reactionchamber, thus the plasma may also contain components of the carrier gas,such as argon or nitrogen ions and/or radicals. Generally, theconcentration of the silicon-containing reactant in the reaction chamberis allowed to decrease substantially prior to striking the plasma. Theflow of nitrogen-containing reactant, and carrier gas if present, sweepsthe excess silicon-containing reactant (that not adsorbed onto thesurface of the substrate) out of the chamber without the need for avacuum purge step, although, in one embodiment, a purge is performedprior to striking the plasma.

In some embodiments, the SiN film produced has an undesirable carboncontent. This in-film carbon may result in electrical leakage and mayrender the film unusable for some dielectric barrier applications.Methods described herein produce SiN films with less than 2% carbon, inone embodiment less than 1% carbon, in yet another embodiment less than0.5% carbon. In some embodiments, the reduction in carbon residue isreadily observable in FTIR spectra. One embodiment is a method offorming a silicon nitride material on a substrate, including: (a)forming a silicon nitride film on the substrate, said formationincluding: (i) providing the substrate in a reaction chamber; (ii)exposing the substrate to a silicon-containing reactant in the vaporphase so that the silicon-containing reactant is adsorbed onto thesurface of the substrate; (iii) exposing the substrate to annitrogen-containing reactant in the vapor phase so that thenitrogen-containing reactant is adsorbed onto the surface of thesubstrate; (iv) igniting a plasma while the nitrogen-containing reactantis present in the vapor phase; and then, (b) exposing the siliconnitride film to a hydrogen containing plasma. The hydrogen plasmareduces carbon content of the film. In one embodiment, the hydrogenplasma is generated using hydrogen (H₂) and a carrier gas such asnitrogen, helium or argon.

In general, any method described herein can include heating thesubstrate to between about 50° C. and about 550° C. during formation ofthe SiN film. Certain methods described herein take advantage of athermally removable groups, attached either to a silicon-containingreactant or a nitrogen-containing reactant, in order to lower carboncontent. One embodiment is a method of forming a silicon nitridematerial on a substrate, including: (a) providing the substrate in areaction chamber; (b) providing a carrier gas flow through the reactionchamber; (b) exposing the substrate to a vapor phase flow of anitrogen-containing reactant wherein the nitrogen-containing reactant isadsorbed onto the surface of the substrate and then purging the reactionchamber; (c) exposing the substrate to a vapor phase flow of asilicon-containing reactant wherein the silicon-containing reactant isadsorbed onto the surface of the substrate; (d) igniting a plasma in thereaction chamber after the vapor phase flow of the silicon-containingreactant has ceased; and (e) heating the substrate to between about 200°C. and about 550° C.; where at least one of the nitrogen-containingreactant and the silicon-containing reactant bears one or more of athermally removable group, wherein said thermally removable groupdecomposes at between about 200° C. and about 550° C.

These and other features and advantages of the present invention will bedescribed in more detail below with reference to the associateddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a temporal progression of exemplary phases in a CFDprocess.

FIG. 2 is an exemplary process flow outlining a CFD process for making aSiN film.

FIG. 3 is an exemplary process flow outlining a method of making a SiNfilm.

FIG. 4 is an exemplary process flow outlining a method of making a SiNfilm.

FIG. 5 depicts a CFD processing station.

FIG. 6 depicts a schematic view of a multi-station processing tool

DETAILED DESCRIPTION

Overview

The present disclosure relates to formation of SiN films, particularlyon semiconductor substrates. Methods described herein include ways ofcontrolling the carbon content in SiN films, particularly forminglow-carbon content SiN films, as well as conformal film deposition (CFD)methods of forming SiN films.

Definitions

As used herein, the following definitions shall apply unless otherwiseindicated.

A “silicon-containing reactant” is a reagent, single or mixture ofreagents, used to make a SiN material, where the reagent contains atleast one silicon compound. The silicon compound can be, for example, asilane, a halosilane or an aminosilane. A silane contains hydrogenand/or carbon groups, but does not contain a halogen. Examples ofsilanes are silane (SiH₄), disilane (Si₂H₆), and organo silanes such asmethylsilane, ethylsilane, isopropylsilane, t-butylsilane,dimethylsilane, diethylsilane, di-t-butylsilane, allylsilane,sec-butylsilane, thexylsilane, isoamylsilane, t-butyldisilane,di-t-butyldisilane, and the like. A halosilane contains at least onehalogen group and may or may not contain hydrogens and/or carbon groups.Examples of halosilanes are iodosilanes, bromosilanes, chlorosilanes andfluorosilanes. Although halosilanes, particularly fluorosilanes, mayform reactive halide species that can etch silicon materials, in certainembodiments described herein, the silicon-containing reactant is notpresent when a plasma is struck. Specific chlorosilanes aretetrachlorosilane (SiCl₄), trichlorosilane (HSiCl₃), dichlorosilane(H₂SiCl₂), monochlorosilane (ClSiH₃), chloroallylsilane,chloromethylsilane, dichloromethylsilane, chlorodimethylsilane,chloroethylsilane, t-butylchlorosilane, di-t-butylchlorosilane,chloroisopropylsilane, chloro-sec-butylsilane,t-butyldimethylchlorosilane, thexyldimethylchlorosilane, and the like.An aminosilane includes at least one nitrogen atom bonded to a siliconatom, but may also contain hydrogens, oxygens, halogens and carbons.Examples of aminosilanes are mono-, di-, tri- and tetra-aminosilane(H₃Si(NH₂)₄, H₂Si(NH₂)₂, HSi(NH₂)₃ and Si(NH₂)₄, respectively), as wellas substituted mono-, di-, tri- and tetra-aminosilanes, for example,t-butylaminosilane, methylaminosilane, tert-butylsilanamine,bis(tertiarybutylamino)silane (SiH₂(NHC(CH₃)₃)₂ (BTBAS), tert-butylsilylcarbamate, SiH(CH₃)-(N(CH₃)₂)₂, SiHCl—(N(CH₃)₂)₂, (Si(CH₃)₂NH)₃ andthe like.

A “nitrogen-containing reactant” contains at least one nitrogen, forexample, ammonia, hydrazine, amines (amines bearing carbon) such asmethylamine, dimethylamine, ethylamine, isopropylamine, t-butylamine,di-t-butylamine, cyclopropylamine, sec-butylamine, cyclobutylamine,isoamylamine, 2-methylbutan-2-amine, trimethylamine, diisopropylamine,diethylisopropylamine, di-t-butylhydrazine, as well as aromaticcontaining amines such as anilines, pyridines, and benzylamines. Aminesmay be primary, secondary, tertiary or quaternary (for example,tetraalkylammonium compounds). A nitrogen-containing reactant cancontain heteroatoms other than nitrogen, for example, hydroxylamine,t-butyloxycarbonyl amine and N-t-butyl hydroxylamine arenitrogen-containing reactants.

“Plasma” refers to a plasma ignited in a reaction chamber or remotelyand brought into the reaction chamber. Plasmas can include the reactantsdescribed herein and may include other agents, for example, a carriergas, or reactive species such as hydrogen gas. The reactants and otheragents may be present in a reaction chamber when a plasma is struck, ora remote plasma may be flowed into a chamber where the reactants arepresent and/or the reactants and/or carrier gas may be ignited into aplasma remotely and brought into the reaction chamber. A “plasma” ismeant to include any plasma known to be technologically feasible,including inductively-coupled plasmas and microwave surface waveplasmas. One of ordinary skill in the art would appreciate thatadvancements in technology will occur, and thus as yet developed plasmagenerating techniques are contemplated to be within the scope of theinvention.

“Thermally removable group” refers to a moiety, on either or both of thenitrogen-containing reactant and the silicon-containing reactant, thatbreaks down into volatile components at between about 200° C. and about550° C. Described herein are non-limiting examples such as secondary andtertiary carbon group, which undergo elimination reactions in thistemperature range. One of ordinary skill in the art would recognize thatother groups thermally decompose as described by other mechanisms, forexample, a t-butyloxycarbonyl (t-BOC or “BOC”) group thermallydecomposes via both an elimination mechanism where the t-butyl portionof the group forms isobutylene, but also the decomposition forms carbondioxide. Thus a thermally removable group is not limited to a particularmechanism or combination of mechanisms. As long as the group breaks downunder the specified temperature range to produce at least one volatilecomponent, then it qualifies as a thermally decomposable group. Forexample, under a given set of conditions, t-butylethylamine will undergothermal decomposition of the t-butyl group to form isobutylene while theethyl group remains, and thus isobutylene and ethylamine are theproducts of the thermal decomposition. One of ordinary skill in the artwould recognize that the volatility of a component depends, in part, onthe reaction conditions under which the component is generated. Forexample, isobutylene may be volatile and be removed from a reactionchamber under the conditions of heating and low press because it doesnot react with the adsorbed reactants, while, for example, ammonia,although generally a volatile compound, undergoes reaction with asilicon-containing reactant adsorbed on the surface of a substrate.

Methods

Described herein are methods of making SiN films. In particularembodiments SiN films are made using plasma-activated conformal filmdeposition (CFD). In some embodiments, SiN films are deposited andtreated with a hydrogen plasma to reduce the carbon content of the film.In some embodiments, a silicon-containing reactant and anitrogen-containing reactant are used to make a SiN film, where one orboth of the reactants includes a thermally removable group. In theseembodiments, a hydrogen plasma may not be necessary to remove unwantedcarbon from the film, for example when the carbon content issubstantially embodied by the thermally removable group or groups'volatile component. When the SiN film is heated, the carbon is drivenoff via the thermally removable group or groups breaking down intovolatile components that are removed in the gas phase. In certainembodiments, although some of the carbon content of the SiN film isremoved via exploiting a thermally removable group or groups, there maybe some unwanted carbon remaining, and thus a hydrogen plasma treatmentmay be employed as well. Each of the aforementioned aspects aredescribed in more detail below.

In certain embodiments, CFD is used to deposit the SiN films, althoughmethods described herein are not limited to CFD. Other suitable methodsinclude ALD, PEALD, CVD, PECVD, and plasma enhanced cyclic chemicalvapor deposition (PECCVD). Methods for forming films using CFD aredescribed in U.S. patent application, Ser. No. ______, [Attorney docketNOVLP405] filed on the same day as the instant disclosure, and which isincorporated by reference herein for all purposes. For context, a shortdescription of CFD is provided.

Manufacture of semiconductor devices typically involves depositing oneor more thin films on a non-planar substrate in an integratedfabrication process. In some aspects of the integrated process it may beuseful to deposit conformal thin films. For example, a silicon nitridefilm may be deposited on top of an elevated gate stack to act as aspacer layer for protecting lightly-doped source and drain regions fromsubsequent ion implantation processes.

In spacer layer deposition processes, chemical vapor deposition (CVD)processes may be used to form a silicon nitride film on the non-planarsubstrate, which is then anisotropically etched to form the spacerstructure. However, as a distance between gate stacks decreases, masstransport limitations of CVD gas phase reactions may cause“bread-loafing” deposition effects. Such effects typically exhibitthicker deposition at top surfaces of gate stacks and thinner depositionat the bottom corners of gate stacks. Further, because some die may haveregions of differing device density, mass transport effects across thewafer surface may result in within-die and within-wafer film thicknessvariation. These thickness variations may result in over-etching of someregions and under-etching of other regions. This may degrade deviceperformance and/or die yield.

Some approaches to addressing these issues involve atomic layerdeposition (ALD). In contrast with a CVD process, where thermallyactivated gas phase reactions are used to deposit films, ALD processesuse surface-mediated deposition reactions to deposit films on alayer-by-layer basis. In one example ALD process, a substrate surface,including a population of surface active sites, is exposed to a gasphase distribution of a first reactant (A). Some molecules of reactant Amay form a condensed phase atop the substrate surface, includingchemisorbed species and physisorbed molecules of reactant A. The reactoris then evacuated to remove gas phase and physisorbed reactant A so thatonly chemisorbed species remain. A second film reactant (B) is thenintroduced to the reactor so that some molecules of reactant B adsorb tothe substrate surface. Thermal energy provided to the substrateactivates surface reactions between adsorbed molecules of reactants Aand B, forming a film layer. Finally, the reactor is evacuated to removereaction by-products and unreacted reactant B, ending the ALD cycle.Additional ALD cycles may be included to build film thickness. Plasma,or other energetic means, may be used in conjunction with heating, or asalternatives to heating the substrate in order to drive the reactionbetween reactant A and B.

Depending on the exposure time of the reactant dosing steps and thesticking coefficients of the reactants, each ALD cycle may deposit afilm layer of, in one example, between one-half and three angstromsthick. Thus, ALD processes may be time consuming when depositing filmsmore than a few nanometers thick. Further, some reactants may have longexposure times to deposit a conformal film, which may also reduce waferthroughput time.

Conformal films may also be deposited on planar substrates. For example,antireflective layers for lithographic patterning applications may beformed from planar stacks comprising alternating film types. Suchantireflective layers may be approximately 100 to 1000 angstroms thick,making ALD processes less attractive than CVD processes. However, suchanti-reflective layers may also have a lower tolerance for within-waferthickness variation than many CVD processes may provide. For example, a600-angstrom thick antireflective layer may tolerate a thickness rangeof less than 3 angstroms.

Accordingly, various embodiments described herein include CFD to depositSiN films. Generally, CFD does not rely on complete purges of one ormore reactants prior to reaction to form SiN. For example, there may beone or more reactants present in the vapor phase when a plasma (or otheractivation energy) is struck. Accordingly, one or more of the processsteps described in the ALD process may be shortened or eliminated in anexample CFD process. Further, in some embodiments, plasma activation ofdeposition reactions may result in lower deposition temperatures thanthermally-activated reactions, potentially reducing the thermal budgetof an integrated process.

FIG. 1, shows a temporal progression of exemplary phases in a CFDprocess, 100, for various process parameters, for example, inert gasflow, reactant A, reactant B and when a plasma is struck. In FIG. 1, twodeposition cycles 110A and 110B are shown. One of ordinary skill in theart would appreciate that any suitable number of deposition cycles maybe included in a CFD process to deposit a desired film thickness.Example CFD process parameters include, but are not limited to, flowrates for inert and reactant species, plasma power and frequency,substrate temperature, and process station pressure.

The concept of a CFD “cycle” is relevant to the discussion of variousembodiments herein. Generally a cycle is the minimum set of operationsrequired to perform a surface deposition reaction one time. The resultof one cycle is production of at least a partial film layer on asubstrate surface. Typically, a CFD cycle will include only those stepsnecessary to deliver and adsorb each reactant to the substrate surface,and then react those adsorbed reactants to form the partial layer offilm. Of course, the cycle may include certain ancillary steps such assweeping one of the reactants or byproducts and/or treating the partialfilm as deposited. Generally, a cycle contains only one instance of aunique sequence of operations. As an example, a cycle may include thefollowing operations: (i) delivery/adsorption of reactant A, (ii)delivery/adsorption of reactant B, (iii) sweep B out of the reactionchamber, and (iv) apply plasma to drive a surface reaction of A and B toform the partial film layer on the surface.

Referring to FIG. 1, an inert gas is flowed during all phases of process100. At reactant A exposure phase, 120A, reactant A is supplied at acontrolled flow rate to a process station to saturate exposed surfacesof a substrate. Reactant A may be any suitable deposition reactant, forexample, a nitrogen-containing reactant. In the embodiment shown in FIG.1, reactant A flows continuously throughout deposition cycles 110A and110B. Unlike a typical ALD process, where film precursor (reactant)exposures are separated to prevent gas phase reaction, reactants A and Bmay be allowed to mingle in the gas phase of some embodiments of a CFDprocess. Continuously supplying reactant A to the process station mayreduce or eliminate a reactant A flow rate turn-on and stabilizationtime compared to an ALD process where reactant A is first turned on,then stabilized and exposed to the substrate, then turned off, andfinally removed from a reactor. While the embodiment shown in FIG. 1depicts reactant A exposure phase 120A as having a constant flow rate,it will be appreciated that any suitable flow of reactant A, including avariable flow, may be employed within the scope of the presentdisclosure. In some embodiments, reactant A exposure phase 120A may havea duration that exceeds a substrate surface saturation time for reactantA. For example, the embodiment of FIG. 1 includes a reactant Apost-saturation exposure time 130 in reactant A exposure phase 120A.Optionally, reactant A exposure phase 120A may include a controlled flowrate of an inert gas. Example inert gases include, but are not limitedto, nitrogen, argon, and helium. The inert gas may be provided to assistwith pressure and/or temperature control of the process station,evaporation of a liquid reactant, more rapid delivery of the reactantand/or as a sweep gas for removing process gases from the processstation and/or process station plumbing.

At Reactant B exposure phase 140A of the embodiment shown in FIG. 1,reactant B is supplied at a controlled flow rate to the process stationto saturate the exposed substrate surface. In this example, reactant Bis a silicon-containing reactant. While the embodiment of FIG. 1 depictsreactant B exposure phase 140A as having a constant flow rate, it willbe appreciated that any suitable flow of reactant B, including avariable flow, may be employed within the scope of the presentdisclosure. Further, it will be appreciated that reactant B exposurephase 140A may have any suitable duration. In some embodiments, reactantB exposure phase 140A may have a duration exceeding a substrate surfacesaturation time for reactant B. For example, the embodiment shown inFIG. 1 depicts a reactant B post-saturation exposure time 15 included inreactant B exposure phase 140A.

In some embodiments, surface adsorbed B species may exist asdiscontinuous islands on the substrate surface, making it difficult toachieve surface saturation of reactant B. Various surface conditions maydelay nucleation and saturation of reactant B on the substrate surface.For example, ligands released on adsorption of reactants A and/or B mayblock some surface active sites, preventing further adsorption ofreactant B. Accordingly, in some embodiments, continuous adlayers ofreactant B may be provided by modulating a flow of and/or discretelypulsing reactant B into the process station during reactant B exposurephase 140A. This may provide extra time for surface adsorption anddesorption processes while conserving reactant B compared to a constantflow scenario. Additionally, or alternatively, in some embodiments, oneor more sweep phases may be included between consecutive exposures ofreactant B.

Prior to activation of the plasma, gas phase reactant B may be removedfrom the process station in sweep phase 160A in some embodiments.Sweeping the process station may avoid gas phase reactions wherereactant B is unstable to plasma activation or where unwanted speciesmight be formed. Further, sweeping the process station may removesurface adsorbed ligands that may otherwise remain and contaminate thefilm. Example sweep gases may include, but are not limited to, argon,helium, and nitrogen. In the embodiment shown in FIG. 1, sweep gas forsweep phase 160A is supplied by the continuous inert gas stream. In someembodiments, sweep phase 160A may include one or more evacuationsubphases for evacuating the process station. Alternatively, it will beappreciated that sweep phase 160A may be omitted in some embodiments.

Sweep phase 160A may have any suitable duration. In some embodiments,increasing a flow rate of a one or more sweep gases may decrease theduration of sweep phase 160A. For example, a sweep gas flow rate may beadjusted according to various reactant thermodynamic characteristicsand/or geometric characteristics of the process station and/or processstation plumbing for modifying the duration of sweep phase 160A. In onenon-limiting example, the duration of a sweep phase may be optimized byadjustment of the sweep gas flow rate. This may reduce deposition cycletime, which may improve substrate throughput.

At plasma activation phase 180A of the embodiment shown in FIG. 1,plasma energy is provided to activate surface reactions between surfaceadsorbed reactants A and B. For example, the plasma may directly orindirectly activate gas phase molecules of reactant A to form reactant Aradicals. These radicals may then interact with surface adsorbedreactant B, resulting in film-forming surface reactions. Plasmaactivation phase 180A concludes deposition cycle 110A, which in theembodiment of FIG. 1 is followed by deposition cycle 110B, commencingwith reactant A exposure phase 120B.

In some embodiments, the plasma ignited in plasma activation phase 180Amay be formed directly above the substrate surface. This may provide agreater plasma density and enhance a surface reaction rate betweenreactants A and B. For example, plasmas for CFD processes may begenerated by applying a radio frequency (RF) field to a low-pressure gasusing two capacitively coupled plates. Any suitable gas may be used toform the plasma. In this example, the inert gas such as argon or heliumis used along with reactant A, a nitrogen-containing reactant, to formthe plasma. Ionization of the gas between the plates by the RF fieldignites the plasma, creating free electrons in the plasma dischargeregion. These electrons are accelerated by the RF field and may collidewith gas phase reactant molecules. Collision of these electrons withreactant molecules may form radical species that participate in thedeposition process. It will be appreciated that the RF field may becoupled via any suitable electrodes. Non-limiting examples of electrodesinclude process gas distribution showerheads and substrate supportpedestals. It will be appreciated that plasmas for CFD processes may beformed by one or more suitable methods other than capacitive coupling ofan RF field to a gas.

Plasma activation phase 180A may have any suitable duration. In someembodiments, plasma activation phase 180A may have a duration thatexceeds a time for plasma-activated radicals to interact with allexposed substrate surfaces and adsorbates, forming a continuous filmatop the substrate surface. For example, the embodiment shown in FIG. 1includes a plasma post-saturation exposure time 190 in plasma activationphase 180A.

In some embodiments, extending a plasma exposure time and/or providing aplurality of plasma exposure phases may provide a post-reactiontreatment of bulk and/or near-surface portions of the deposited film. Inone embodiment, decreasing surface contamination may prepare the surfacefor adsorption of reactant A. For example, a silicon nitride film formedfrom reaction of a silicon-containing reactant and a nitrogen-containingreactant may have a surface that may resist adsorption of subsequentreactants. Treating the silicon nitride surface with a plasma may createhydrogen bonds for facilitating subsequent adsorption and reactionevents. The SiN films described herein can be exposed toother-than-plasma treatments.

In some embodiments, a treatment other than a plasma treatment isemployed to modify the properties the as deposited film. Such treatmentsinclude electromagnetic radiation treatments, thermal treatments (e.g.,anneals or high temperature pulses), and the like. Any of thesetreatments may be performed alone or in combination with anothertreatment, including a plasma treatment. Any such treatment can beemployed as a substitute for any of the above-described plasmatreatments. In a specific embodiment, the treatment involves exposingthe film to ultraviolet radiation. As described below, in a specificembodiment, the method involves the application of UV-radiation to afilm in situ (i.e., during formation of the film) or post deposition ofthe film. Such treatment serves to reduce or eliminate defect structureand provide improved electrical performance.

In certain specific embodiments, a UV treatment can be coupled with aplasma treatment. These two operations can be performed concurrently orsequentially. In the sequential option, the UV operation optionallytakes place first. In the concurrent option, the two treatments may beprovided from separate sources (e.g., an RF power source for the plasmaand a lamp for the UV) or from a single source such as a helium plasmathat produces UV radiation as a byproduct.

In some embodiments, film properties, such as film stress, dielectricconstant, refractive index, etch rate may be adjusted by varying plasmaparameters.

While many examples discussed herein include two reactants (A and B), itwill be appreciated that any suitable number of reactants may beemployed within the scope of the present disclosure. In someembodiments, a single reactant and an inert gas used to supply plasmaenergy for a surface reaction can be used. Alternatively, someembodiments may use multiple reactants to deposit a film. For example,in some embodiments, a silicon nitride film may be formed by reaction ofa silicon-containing reactant and one or more of a nitrogen-containingreactant, or one or more silicon-containing reactants and a singlenitrogen-containing reactant, or more than one of both thesilicon-containing reactant and the nitrogen-containing reactant.

When multiple reactants are employed and the flow of one of them iscontinuous, at least two of them will co-exist in the gas phase during aportion of the CFD cycle. Similarly, when no purge step is performedafter delivery of the first reactant, two reactants will co-exist in thereaction chamber. Therefore, it may be important to employ reactantsthat do not appreciably react with one another in the gas phase absentapplication of activation energy. Typically, the reactants should notreact until present on the substrate surface and exposed to plasma oranother appropriate non-thermal activation condition. Choosing suchreactants involves considerations of at least (1) the thermodynamicfavorability (Gibb's free energy <0) of the desired reaction, and (2)the activation energy for the reaction, which should be sufficientlygreat so that there is negligible reaction at the desired depositiontemperature.

Selection of one or more reactants may be driven by various film and/orhardware considerations. For example, in some embodiments, a siliconnitride film may be formed from reaction of dichlorosilane and aplasma-activated nitrogen-containing reactant, for example ammonia.Chemisorption of dichlorosilane to a silicon surface (indicated by therectangle in Scheme 1, etc.) may create a silicon-hydrogen terminatedsurface, liberating hydrogen chloride (HCl). An example of thischemisorption reaction is depicted in Scheme 1.

The cyclic intermediate shown in Scheme 1 may then be transformed into asilicon amide terminated surface via reaction with the same or differentplasma-activated nitrogen-containing reactant.

However, some molecules of dichlorosilane may chemisorb by alternativemechanisms. For example, surface morphology may hinder the formation ofthe cyclic intermediate depicted in Scheme 1. An example of anotherchemisorption mechanism is shown Scheme 2. During subsequent plasmaactivation of a nitrogen-containing reactant, the remaining chlorineatom of the adsorbed intermediate species shown in Scheme 2 may beliberated and may become activated by the plasma. This may cause etchingof the silicon nitride surface, potentially causing the silicon nitridefilm to become rough or hazy. Further, the residual chlorine atom mayreadsorb, physically and/or chemically, potentially contaminating thedeposited film. This contamination may alter physical and/or electricalproperties of the silicon nitride film. Further still, the activatedchlorine atom may cause etch damage to portions of the process stationhardware, potentially reducing the service life of portions of theprocess station. Also, excess chloride content of the film may beunwanted.

Thus, in some embodiments, a monochlorosilane is used rather than adichlorosilane. This may reduce film contamination, film damage, and/orprocess station damage. An example of the chemisorption of chlorosilaneis shown in Scheme 3. While the example depicted in Scheme 3 useschlorosilane as the silicon-containing reactant, it will be appreciatedthat any suitable monosubstituted halosilane may be used. For examplethere may be applications where a certain carbon content is desirable.In one embodiment, the carbon content of the SiN film is tailored bychoice of carbon containing groups, both carbon amount and type, on oneor both of the silicon containing reactant and the nitrogen-containingreactant.

As explained above, the depicted intermediate structures may react witha nitrogen-containing reactant to form a silicon amide terminatedsurface. For example, ammonia may be activated by a plasma, formingvarious ammonia radical species. The radical species react with theintermediate, forming the silicon amide terminated surface. Ammonia is acommon nitrogen-containing reactant for forming SiN films. Certainembodiments described herein utilize ammonia as a nitrogen-containingreactant.

However, ammonia may physisorb strongly to surfaces of the reactantdelivery lines, process station, and exhaust plumbing, which may lead toextended purge and evacuation times. Further, ammonia may have a highreactivity with some gas phase silicon-containing reactants. For examplegas-phase mixtures of dichlorosilane (SiH₂Cl₂) and ammonia may createunstable species such as diaminosilane (SiH₂(NH₂)₂). Such species maydecompose in the gas phase, nucleating small particles. Small particlesmay also be formed if ammonia reacts with hydrogen chloride, generatedduring chemisorption of a halosilane, to form ammonium chloride. Suchparticles may accumulate in the process station where they maycontaminate substrate surfaces, potentially leading to integrated devicedefects, and where they may contaminate process station hardware,potentially leading to tool down time and cleaning. The small particlesmay also accumulate in exhaust plumbing, may clog pumps and blowers, andmay create a need for special environmental exhaust scrubbers and/orcold traps.

Thus, in some embodiments, an amine may be used rather than anitrogen-containing reactant that does not contain carbon. For example,various radicals formed from plasma activation of alkyl amines, such ast-butyl amine, may be supplied to the process station. Substitutedamines, such as t-butyl amine, may have a lower sticking coefficient onprocess hardware than ammonia, which may result in comparatively lowerphyisorbption rates and comparatively lower process purge time.

Further, such alkyl amines form halogenated salts that are more volatilethan ammonium salts, for example ammonium chloride. For example,t-butylammonium chloride is substantially more volatile than ammoniumchloride and thus less deposits are formed on the interior of thechamber and associated plumbing and deposition hardware. This reducestool down time, device defect creation, and environmental abatementexpense.

In other embodiments, the nitrogen-containing reactant is an amine,having a carbon component and a nitrogen component. In some embodiments,the amine serves as a source of ammonia. That is, for example,t-butylamine is the nitrogen-containing reactant, but after processing,the t-butyl portion of the reactant is volatized and removed from theSiN film, while the amine portion (ammonia) is incorporated into the SiNfilm. In this way, the nitrogen-containing reactant serves as a deliveryvector for ammonia, or an “ammonia equivalent.” This avoids having thereaction chamber and associated plumbing and hardware exposed to excessammonia (although some ammonia is inevitably lost from the SiN filmduring decomposition of the t-butyl group and may contact the reactorand other surfaces). Further still, certain amines (nitrogen-containingreactants) may react with silicon-containing reactants to form a newsilicon-containing reactant. For example, the reaction of t-butyl aminewith dichlorosilane may form BTBAS. Although BTBAS contains silicon, italso contains nitrogen (by convention defined herein, this is asilicon-containing reactant). Because t-butyl amine decomposes attemperatures above 300° C. to form isobutylene and ammonia, analogouslyBTBAS may thermally decompose to form SiN and (2 moles of) isobutylene(BTBAS may also be preformed and used as a silicon-containing reactantwith a nitrogen-containing reactant). Thus, certain amines providealternate routes to form silicon nitride. Described herein are methodsof exploiting such alkyl amines.

In some embodiments, where thermal decomposition pathways are exploited,the thermally removable group need not be part of a nitrogen-containingreactant. For example, in certain embodiments the thermally removablegroup is part of the silicon-containing reactant. In one embodiment thethermally removable group is directly attached to a silicon, nitrogen oroxygen of a silicon-containing reactant. In some embodiments, thereactant, nitrogen or silicon, includes a thermally removable group andat least one group that does not thermally decompose. This may bedesirable, for example, when a certain carbon content in the final SiNfilm is desired, or, for example, when it is desirable to tailor themanner in which the carbon is removed from the SiN film. For example, inone embodiment, among the nitrogen and silicon-containing reactants,there is included both a thermally removable group and a non-thermallyremovable group, i.e., one that does not thermally decompose under thesame conditions. In this way a SiN film is produced where some of thecarbon can be removed, if desired, via thermal decomposition and theremainder of the carbon removed, if desirable, via, for example,hydrogen plasma treatment. Thus methods of the invention contemplatecarbon removal from a single film in more than one way.

Each of the aforementioned aspects are described in more detail below.

As described above, in one embodiment, CFD is used to make SiN films.One embodiment is a method of forming a silicon nitride material on asubstrate, including: (a) providing the substrate in a reaction chamber;(b) continuously exposing the substrate to a vapor phase flow of anitrogen-containing reactant wherein the nitrogen-containing reactant isadsorbed onto the surface of the substrate; (c) periodically exposingthe substrate to a vapor phase flow of a silicon-containing reactantwherein the silicon-containing reactant is adsorbed onto the surface ofthe substrate; and (d) periodically igniting a plasma in the reactionchamber when the vapor phase flow of the silicon-containing reactant hasceased. In this embodiment, the plasma is ignited to form a plasma fromthe nitrogen-containing reactant flowing in the reaction chamber. In oneembodiment, a carrier gas is flowed continuously through the reactionchamber, thus the plasma may also contain components of the carrier gas,such as argon or nitrogen ions and/or radicals. Generally, theconcentration of the silicon-containing reactant in the reaction chamberis allowed to decrease substantially prior to striking the plasma. Theflow of nitrogen-containing reactant, and carrier gas if present, sweepsthe excess silicon-containing reactant (that not adsorbed onto thesurface of the substrate) out of the chamber without the need for avacuum purge step, although, in one embodiment, a purge is performedprior to striking the plasma.

FIG. 2 depicts an exemplary process flow, 200, outlining aspects of themethod. A substrate is provided to the chamber, see 205. A flow ofnitrogen-containing reactant is established and continued throughout200, see 210. The substrate is periodically exposed to asilicon-containing reactant, see 215. Also, periodically, a plasma isstruck, but only when the silicon-containing reactant flow has ceased.In one embodiment, the silicon-containing reactant not adsorbed to thesurface of the substrate is swept out of the chamber by the flow of theinert gas and/or nitrogen-containing reactant. In another embodiment, apurge may be used. After the plasma treatment, the method is complete.The steps may be repeated a number of times to build up a layer ofdesired thickness.

In one embodiment, using any of the methods described herein, thesemi-conductor wafer is heated to between about 50° C. and about 550° C.In one embodiment, the wafer is heated throughout the deposition, inother embodiments the wafer is heated periodically during the depositionor after the deposition steps as an anneal. Heating may also be used inconjunction with thermally removable groups as described in more detailbelow.

The method is particularly useful for forming SiN films on semiconductorwafers. In one embodiment, steps (b) through (d) are repeated to form aconformal layer on the semiconductor wafer between about 1 nm and about100 nm thick. In another embodiment, between about 5 nm and about 50 nmthick. In another embodiment, between about 5 nm and about 30 nm thick.

For the methods described herein, generally any silicon-containingreactant is suitable. The SiN material of the films produced may or maynot contain carbon. The carbon in the SiN film may come from thesilicon-containing reactant or the nitrogen-containing reactant. In oneembodiment, the silicon-containing reactant is selected from the groupconsisting of a silane, a halosilane and an aminosilane, and mixturesthereof. In one embodiment, the silicon-containing reactant is ahalosilane, an aminosilane or a mixture thereof. In one embodiment, thesilicon-containing reactant is a halosilane. In one embodiment, thehalosilane is a chlorosilane. In one embodiment, the halosilane is amono- or dihalosilane, for example a monochlorosilane or adichlorosilane. In a particular embodiment, the halosilane is amonochlorosilane. In one embodiment, the monochlorosilane ischlorosilane.

In certain embodiments, a silicon-containing reactant is paired with aparticular nitrogen-containing reactant. For example, a monochlorosilaneis paired with an alkyl amine, for example t-butyl amine, to make SiNfilms using the methods described herein. In one embodiment,dichlorosilane is used with t-butylamine to make SiN using a methoddescribed herein.

For methods described herein, the nitrogen-containing reactant can beany suitable nitrogen-containing reactant. In one embodiment, thenitrogen-containing reactant is selected from the group consisting ofammonia, a hydrazine, an amine and mixtures thereof. In one embodiment,the nitrogen-containing reactant includes a C₁₋₁₀ alkyl amine or amixture of C₁₋₁₀ alkyl amines. In one embodiment, the C₁₋₁₀ alkyl amineis a primary alkyl amine or a secondary alkyl amine. In one embodiment,the C₁₋₁₀ alkyl amine is a primary alkyl amine. In one embodiment, theC₁₋₁₀ alkyl amine is according to formula I:

-   -   wherein each of R¹, R² and R³ is, independent of the others, H        or C₁₋₃ alkyl; or two of R¹, R² and R³, together with the carbon        atom to which they are attached form form a C₃₋₇ cycloalkyl and        the other of R¹, R² and R³ is H or C₁₋₃ alkyl. In one        embodiment, the C₁₋₁₀ alkyl amine has a secondary or tertiary        carbon attached directly to the nitrogen. In one embodiment, the        C₁₋₁₀ alkyl amine is selected from the group consisting of        isopropylamine, cyclopropylamine, sec-butylamine, tert-butyl        amine, cyclobutylamine, isoamylamine, 2-methylbutan-2-amine and        thexylamine (2,3-dimethylbutan-2-amine). In one embodiment, in        the C₁₋₁₀ alkyl amine of Formula I, each of R¹, R² and R³ is        C₁₋₃ alkyl. In one embodiment, the C₁₋₁₀ alkyl amine is        tert-butyl amine. TBA is particularly useful for the reasons        described.

In some embodiments, the SiN film produced has an undesirable carboncontent. This in-film carbon may result in electrical leakage and mayrender the film unusable for some dielectric barrier applications.Carbon content can vary, but in some embodiments approximately 10%carbon (by weight) can be considered too high. Methods described hereinaddress unwanted carbon in SiN films. Methods described herein produceSiN films with less than 2% carbon, in one embodiment less than 1%carbon, in yet another embodiment less than 0.5% carbon. In someembodiments, the reduction in carbon residue is readily observable inFTIR spectra, although other analytical methods are known to one ofordinary skill in the art that can measure carbon content in theseranges. One embodiment is a method of forming a silicon nitride materialon a substrate, including: (a) forming a silicon nitride film on thesubstrate, said formation including: (i) providing the substrate in areaction chamber; (ii) exposing the substrate to a silicon-containingreactant in the vapor phase so that the silicon-containing reactant isadsorbed onto the surface of the substrate; (iii) exposing the substrateto an nitrogen-containing reactant in the vapor phase so that thenitrogen-containing reactant is adsorbed onto the surface of thesubstrate; (iv) igniting a plasma while the nitrogen-containing reactantis present in the vapor phase; and then, (b) exposing the siliconnitride film to a hydrogen containing plasma to remove at least somecarbon content of the silicon nitride film.

FIG. 3 depicts an exemplary process flow, 300, outlining aspects of themethod. A substrate is provided to the chamber, see 305. The substrateis exposed to a silicon-containing reactant, see 310. The substrate isexposed to a nitrogen-containing reactant, see 315. A plasma is struckwhile the nitrogen-containing reactant is present in the vapor phase,see 320, thus forming a SiN material is formed on the substrate. In oneembodiment, the silicon-containing reactant not adsorbed to the surfaceof the substrate is swept out of the chamber by the flow of the inertgas and/or nitrogen-containing reactant prior to striking the plasma. Inanother embodiment, a purge may be used to remove vapor phasesilicon-containing reactant. One or more iterations of 310-320 can beperformed to build up a SiN layer. After the SiN film is produced to adesired thickness, the film is exposed to a hydrogen plasma, see 325.After treatment with hydrogen plasma to remove the desired amount ofcarbon, the method is done. In one embodiment, the hydrogen plasma isgenerated using hydrogen (H₂) and a carrier gas such as nitrogen, heliumor argon. Other hydrogen containing gases, or active hydrogen atomsproduced by a remote plasma source, may be used to treat the depositedfilm. Further, in some embodiments, the carbon content of the film maybe tuned to any suitable concentration by varying one or more of thenumber of treatment pulses and their duration, the intensity of thetreatment plasma, the substrate temperature, and the treatment gascomposition.

As described in relation to previous methods, in one embodiment, thesubstrate is a semiconductor wafer. In one embodiment, (ii) is performedprior to (iii). In another embodiment, (iii) is performed prior to (ii).In certain embodiments, (a) is repeated two or more times prior to (b).That is, the hydrogen plasma treatment removes carbon from the SiN film.It is not always necessary to perform the hydrogen plasma treatmentafter each reaction to form SiN, rather, a number of layers of the SiN(with carbon) may be deposited before requiring a hydrogen plasmatreatment. That is, the hydrogen plasma is effective at removing thecarbon after two or more layers are deposited. In one embodiment, (a)and (b) are repeated to form a conformal layer on the semiconductorwafer between about 1 nm and about 100 nm thick, in another embodiment,between about 5 nm and about 50 nm thick, in another embodiment, betweenabout 5 nm and about 30 nm thick.

Methods described above employ hydrogen plasma to reduce carbon contentin a SiN film. Other methods described herein take advantage of athermal decomposable groups, attached either to a silicon-containingreactant or a nitrogen-containing reactant, in order to lower carboncontent. One embodiment is a method of forming a silicon nitridematerial on a substrate, including: (a) providing the substrate in areaction chamber; (b) providing a carrier gas flow through the reactionchamber; (c) exposing the substrate to a vapor phase flow of anitrogen-containing reactant wherein the nitrogen-containing reactant isadsorbed onto the surface of the substrate and then purging the reactionchamber; (d) exposing the substrate to a vapor phase flow of asilicon-containing reactant wherein the silicon-containing reactant isadsorbed onto the surface of the substrate; (e) igniting a plasma in thereaction chamber after the vapor phase flow of the silicon-containingreactant has ceased; and (f) heating the substrate to between about 200°C. and about 550° C.; where at least one of the nitrogen-containingreactant and the silicon-containing reactant bears one or more of athermally removable group, wherein said thermally removable groupdecomposes at between about 200° C. and about 550° C.

FIG. 4 depicts an exemplary process flow, 400, outlining aspects of themethod. A substrate is provided to the chamber, see 405. A carrier flowis established, see 410. The substrate is exposed to anitrogen-containing reactant, see 415. The substrate is exposed to asilicon-containing reactant, see 420. A plasma is ignited after the flowof the silicon-containing reactant is ceased, see 425. This reactionforms SiN. One or more iterations of 410-425 are performed to build alayer of desired thickness. In this method, 415 and 420 are notnecessarily done in the order presented. The nitrogen-containingreactant flow may or may not be continuous. The substrate may be heatedduring formation of the SiN layer, within, or below, the temperaturerange necessary to decompose the thermally removable groups, but atleast at some point after the SiN film is formed, the substrate isheated to between about 200° C. and about 550° C. in order to break downthe thermally removable groups, see 430. After the substrate is heatedsufficient time to remove the desired amount of carbon, the process flowends.

In one embodiment, the substrate is a semiconductor wafer. In oneembodiment, the method further includes repeating (b) through (e) toform a conformal layer on the semiconductor wafer between about 1 nm andabout 100 nm thick. In one embodiment, (f) is performed throughout (b)through (e). The silicon and nitrogen-containing reactants are asdescribed herein, provided at least one of the silicon and thenitrogen-containing reactant includes at least one thermally removablegroup.

A thermally removable group is a group that breaks down into volatilecomponents at between about 200° C. and about 550° C. For example,secondary and particularly tertiary carbon groups can undergoelimination reactions in this temperature range. In a particularexample, t-butyl groups break down to form isobutylene in thistemperature range. For example, t-butylamine, when heated, undergoes anelimination reaction to form isobutylene and ammonia as depicted inScheme 4. As another example, t-butoxycarbonyl groups (t-BOC) groupsalso thermally decompose, for example at about 150° C., to formisobutylene, carbon dioxide and the

radical to which the t-BOC group was attached. For example, as depictedin Scheme 5, t-butylcarbamate thermally decomposes to give isobutyleneammonia and carbon dioxide. The thermally removable group need not be onthe nitrogen-containing reactant. For example, t-butylsilane,

when heated, also undergoes an elimination reaction to form isobutyleneand a silane. In another example, tert-butyl silylcarbamate thermallydecomposes to form isobutylene, silanamine and carbon dioxide, asdepicted in Scheme 6.

Thus one or more thermally removable groups can be used on thesilicon-containing reactant, the nitrogen-containing reactant, or both.Thus the semiconductor wafer is heated to between about 200° C. andabout 550° C. so that such groups decompose and release their carboncontent and thus reduce the carbon content of the SiN film. Thereactants are adsorbed onto the substrate, a plasma is used to convertthe reactants to a SiN material. Remaining carbon groups are removed byheating the substrate. The heating can be performed during the entiredeposition or periodically to decompose the thermally removable groups.In one embodiment, the substrate is heated to between about 200° C. andabout 550° C., in another embodiment between about 350° C. and about550° C., in another embodiment between about 450° C. and about 550° C.,and in another embodiment, between about 450° C. and about 500° C. Inone embodiment, for example where TBA is used, the SiN film is heated tobetween about 450° C. and about 500° C., for between about 1 second andabout 30 seconds, or between about 1 second and about 20 seconds, orbetween about 1 second and about 10 seconds. Although any particularthermally removable group will breakdown at a certain temperaturethreshold, a higher temperature may be used to increase the rate ofdecomposition and/or as an anneal to improve the properties of the SiNfilm.

As described above, the thermally removable group may include asecondary or tertiary carbon functionality, and either or both of thesilicon-containing reactant and the nitrogen-containing reactant caninclude one or more of the same or different thermally removable groups.In one embodiment, the thermally removable group is according to FormulaII:

wherein each of R¹, R² and R³ is, independent of the others, H or C₁₋₃alkyl; or two of R¹, R² and R³, together with the carbon atom to whichthey are attached form form a C₃₋₇ cycloalkyl and the other of R¹, R²and R³ is H or C₁₋₃ alkyl; and where each of said thermally removablegroup, when part of the nitrogen-containing reactant, is attached to anitrogen or an oxygen of the nitrogen-containing reactant, and, whenpart of the silicon-containing reactant, is attached to a silicon or anitrogen or an oxygen of the silicon-containing reactant. In oneembodiment, each of R¹, R² and R³ is, independent of the others, C₁₋₃alkyl. In one embodiment, the thermally removable group is a t-butylgroup.

One embodiment is a SiN film produced by a method described herein.

Apparatus

Another aspect of the invention is an apparatus configured to accomplishthe methods described herein. A suitable apparatus includes hardware foraccomplishing the process operations and a system controller havinginstructions for controlling process operations in accordance with thepresent invention.

It will be appreciated that any suitable process station may be employedwith one or more of the embodiments described above. For example, FIG. 5schematically shows a CFD process station 1300. For simplicity, CFDprocess station 1300 is depicted as a standalone process station havinga process chamber body 1302 for maintaining a low-pressure environment.However, it will be appreciated that a plurality of CFD process stations1300 may be included in a common low-pressure process tool environment.While the embodiment depicted in FIG. 5 shows one process station, itwill be appreciated that, in some embodiments, a plurality of processstations may be included in a processing tool. For example, FIG. 6depicts an embodiment of a multi-station processing tool 2400. Further,it will be appreciated that, in some embodiments, one or more hardwareparameters of CFD process station 1300, including those discussed indetail below, may be adjusted programmatically by one or more computercontrollers.

A CFD process station 1300 fluidly communicates with reactant deliverysystem 1301 for delivering process gases to a distribution showerhead1306. Reactant delivery system 1301 includes a mixing vessel 1304 forblending and/or conditioning process gases for delivery to showerhead1306. One or more mixing vessel inlet valves 1320 may controlintroduction of process gases to mixing vessel 1304.

Some reactants, like BTBAS, may be stored in liquid form prior tovaporization at and subsequent delivery to the process station. Forexample, the apparatus of FIG. 5 includes a vaporization point 1303 forvaporizing liquid reactant to be supplied to mixing vessel 1304. In someembodiments, vaporization point 1303 may be a heated vaporizer. Thesaturated reactant vapor produced from such vaporizers may condense indownstream delivery piping. Exposure of incompatible gases to thecondensed reactant may create small particles. These small particles mayclog piping, impede valve operation, contaminate substrates, etc. Someapproaches to addressing these issues involve sweeping and/or evacuatingthe delivery piping to remove residual reactant. However, sweeping thedelivery piping may increase process station cycle time, degradingprocess station throughput. Thus, in some embodiments, delivery pipingdownstream of vaporization point 1303 is heat traced. In some examples,mixing vessel 1304 is also heat traced. In one non-limiting example,piping downstream of vaporization point 1303 has an increasingtemperature profile extending from approximately 100° C. toapproximately 150° C. at mixing vessel 1304.

In some embodiments, reactant liquid is vaporized at a liquid injector.For example, a liquid injector may inject pulses of a liquid reactantinto a carrier gas stream upstream of the mixing vessel. In oneembodiment, a liquid injector vaporizes reactant by flashing the liquidfrom a higher pressure to a lower pressure. In another embodiment, aliquid injector atomizes the liquid into dispersed microdroplets thatare subsequently vaporized in a heated delivery pipe. It will beappreciated that smaller droplets may vaporize faster than largerdroplets, reducing a delay between liquid injection and completevaporization. Faster vaporization may reduce a length of pipingdownstream from vaporization point 1303. In one embodiment, a liquidinjector is mounted directly to mixing vessel 1304. In anotherembodiment, a liquid injector is mounted directly to showerhead 1306.

In some embodiments, a liquid flow controller upstream of vaporizationpoint 1303 is provided for controlling a mass flow of liquid forvaporization and delivery to process station 1300. In one example, theliquid flow controller (LFC) includes a thermal mass flow meter (MFM)located downstream of the LFC. A plunger valve of the LFC is adjustedresponsive to feedback control signals provided by aproportional-integral-derivative (PID) controller in electricalcommunication with the MFM. However, it may take one second or more tostabilize liquid flow using feedback control. This may extend a time fordosing a liquid reactant. Thus, in some embodiments, the LFC isdynamically switched between a feedback control mode and a directcontrol mode. In some embodiments, the LFC is dynamically switched froma feedback control mode to a direct control mode by disabling a sensetube of the LFC and the PID controller.

Showerhead 1306 distributes process gases toward substrate 1312. In theembodiment shown in FIG. 13, substrate 1312 is located beneathshowerhead 1306, and is shown resting on a pedestal 1308. It will beappreciated that showerhead 1306 may have any suitable shape, and mayhave any suitable number and arrangement of ports for distributingprocesses gases to substrate 1312.

In some embodiments, a microvolume 1307 is located beneath showerhead1306. Performing a CFD process in a microvolume rather than in theentire volume of a process station may reduce reactant exposure andsweep times, may reduce times for altering CFD process conditions (e.g.,pressure, temperature, etc.), may limit an exposure of process stationrobotics to process gases, etc. Example microvolume sizes include, butare not limited to, volumes between 0.1 liter and 2 liters.

In some embodiments, pedestal 1308 may be raised or lowered to exposesubstrate 1312 to microvolume 1307 and/or to vary a volume ofmicrovolume 1307. For example, in a substrate transfer phase, pedestal1308 is lowered to allow substrate 1312 to be loaded onto pedestal 1308.During a CFD process phase, pedestal 1308 is raised to positionsubstrate 1312 within microvolume 1307. In some embodiments, microvolume1307 completely encloses substrate 1312 as well as a portion of pedestal1308 to create a region of high flow impedance during a CFD process.

Optionally, pedestal 1308 may be lowered and/or raised during portionsthe CFD process to modulate process pressure, reactant concentration,etc., within microvolume 1307. In one embodiment where process chamberbody 1302 remains at a base pressure during the CFD process, loweringpedestal 1308 allows microvolume 1307 to be evacuated. Example ratios ofmicrovolume to process chamber volume include, but are not limited to,volume ratios between 1:500 and 1:10. It will be appreciated that, insome embodiments, pedestal height may be adjusted programmatically by asuitable computer controller.

In another embodiment, adjusting a height of pedestal 1308 allows aplasma density to be varied during plasma activation and/or treatmentcycles included in the CFD process. At the conclusion of the CFD processphase, pedestal 1308 is lowered during another substrate transfer phaseto allow removal of substrate 1312 from pedestal 1308.

While the example microvolume variations described herein refer to aheight-adjustable pedestal, it will be appreciated that, in someembodiments, a position of showerhead 1306 may be adjusted relative topedestal 1308 to vary a volume of microvolume 1307. Further, it will beappreciated that a vertical position of pedestal 1308 and/or showerhead1306 may be varied by any suitable mechanism. One of ordinary skill inthe art would appreciate that such mechanism would include, for example,hydraulics, pneumatics, spring mechanisms, solenoids and the like. Insome embodiments, pedestal 1308 may include a rotational mechanis, forexample along an axis perpendicular to the surface of the substrate, forrotating an orientation of substrate 1312. It will be appreciated that,in some embodiments, one or more of these example adjustments may beperformed programmatically by one or more suitable computer controllers.

Returning to the embodiment shown in FIG. 5, showerhead 1306 andpedestal 1308 electrically communicate with RF power supply 1314 andmatching network 1316 for powering a plasma. In some embodiments, theplasma energy is controlled by controlling one or more of a processstation pressure, a gas concentration, an RF source power, an RF sourcefrequency, and a plasma power pulse timing. For example, RF power supply1314 and matching network 1316 may be operated at any suitable power toform a plasma having a desired composition of radical species. Examplesof suitable powers include, but are not limited to, powers between 100 Wand 5000 W. Likewise, RF power supply 1314 may provide RF power of anysuitable frequency. In some embodiments, RF power supply 1314 may beconfigured to control high- and low-frequency RF power sourcesindependently of one another. Example low-frequency RF frequencies mayinclude, but are not limited to, frequencies between 50 kHz and 500 kHz.Example high-frequency RF frequencies may include, but are not limitedto, frequencies between 1.8 MHz and 2.45 GHz. It will be appreciatedthat any suitable parameters may be modulated discretely or continuouslyto provide plasma energy for the surface reactions. In one non-limitingexample, the plasma power may be intermittently pulsed to reduce ionbombardment with the substrate surface relative to continuously poweredplasmas.

In some embodiments, the plasma is monitored in-situ by one or moreplasma monitors. In one embodiment, plasma power is monitored by one ormore voltage, current sensors (e.g., VI probes). In another embodiment,plasma density and/or process gas concentration is measured by one ormore optical emission spectroscopy sensors (OES). In some embodiments,one or more plasma parameters are programmatically adjusted based onmeasurements from such in-situ plasma monitors. For example, an OESsensor may be used in a feedback loop for providing programmatic controlof plasma power. It will be appreciated that, in some embodiments, othermonitors may be used to monitor the plasma and other processcharacteristics. Such monitors include, but are not limited to, infrared(IR) monitors, acoustic monitors, and pressure transducers.

In some embodiments, the plasma is controlled via input/output control(IOC) sequencing instructions. For example, the instructions for settingplasma conditions for a plasma process phase may be included in acorresponding plasma activation recipe phase of a CFD process recipe. Insome embodiments, process recipe phases may be sequentially arranged, sothat all instructions for a CFD process phase are executed concurrentlywith that process phase. It will be appreciated that some aspects ofplasma generation may have well-characterized transient and/orstabilization times that may prolong a plasma process phase. Put anotherway, such time delays may be predictable. Such time delays may include atime to strike the plasma and a time to stabilize the plasma at theindicted power setting.

In some embodiments, pedestal 1308 may be temperature controlled viaheater 1310. Further, in some embodiments, pressure control for CFDprocess station 1300 may be provided by butterfly valve 1318. As shownin FIG. 5, butterfly valve 1318 throttles a vacuum provided by adownstream vacuum pump (not shown). However, in some embodiments,pressure control of process station 1300 may also be adjusted by varyinga flow rate of one or more gases introduced to CFD process station 1300.

As described above, one or more process stations may be included in amulti-station processing tool. FIG. 6 shows a schematic view of amulti-station processing tool, 2400, with an inbound load lock 2402 andan outbound load lock 2404, either or both of which may comprise aremote plasma source. A robot 2406, at atmospheric pressure, isconfigured to move wafers from a cassette loaded through a pod 2408 intoinbound load lock 2402 via an atmospheric port 2410. A wafer is placedby the robot 2406 on a pedestal 2412 in the inbound load lock 2402, theatmospheric port 2410 is closed, and the load lock is pumped down. Wherethe inbound load lock 2402 comprises a remote plasma source, the wafermay be exposed to a remote plasma treatment in the load lock prior tobeing introduced into a processing chamber 2414. Further, the wafer alsomay be heated in the inbound load lock 2402 as well, for example, toremove moisture and adsorbed gases. Next, a chamber transport port 2416to processing chamber 2414 is opened, and another robot (not shown)places the wafer into the reactor on a pedestal of a first station shownin the reactor for processing. While the embodiment depicted in FIG. 6includes load locks, it will be appreciated that, in some embodiments,direct entry of a wafer into a process station may be provided.

The depicted processing chamber 2414 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 6. Each station hasa heated pedestal (shown at 2418 for station 1), and gas line inlets. Itwill be appreciated that in some embodiments, each process station mayhave different or multiple purposes. For example, in some embodiments, aprocess station may be switchable between a CFD and PECVD process mode.Additionally or alternatively, in some embodiments, processing chamber2414 may include one or more matched pairs of CFD and PECVD processstations. While the depicted processing chamber 2414 comprises fourstations, it will be understood that a processing chamber according tothe present disclosure may have any suitable number of stations. Forexample, in some embodiments, a processing chamber may have five or morestations, while in other embodiments a processing chamber may have threeor fewer stations.

FIG. 6 also depicts a wafer handling system 2490 for transferring waferswithin processing chamber 2414. In some embodiments, wafer handlingsystem 2490 may transfer wafers between various process stations and/orbetween a process station and a load lock. It will be appreciated thatany suitable wafer handling system may be employed. Non-limitingexamples include wafer carousels and wafer handling robots. FIG. 6 alsodepicts a system controller 2450 employed to control process conditionsand hardware states of process tool 2400. System controller 2450 mayinclude one or more memory devices 2456, one or more mass storagedevices 2454, and one or more processors 2452. Processor 2452 mayinclude a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc.

In some embodiments, system controller 2450 controls all of theactivities of process tool 2400. System controller 2450 executes systemcontrol software 2458 stored in mass storage device 2454, loaded intomemory device 2456, and executed on processor 2452. System controlsoftware 2458 may include instructions for controlling the timing,mixture of gases, chamber and/or station pressure, chamber and/orstation temperature, wafer temperature, target power levels, RF powerlevels, substrate pedestal, chuck and/or susceptor position, and otherparameters of a particular process performed by process tool 2400.System control software 2458 may be configured in any suitable way. Forexample, various process tool component subroutines or control objectsmay be written to control operation of the process tool componentsnecessary to carry out various process tool processes. System controlsoftware 2458 may be coded in any suitable computer readable programminglanguage.

In some embodiments, system control software 2458 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. For example, each phase of a CFDprocess may include one or more instructions for execution by systemcontroller 2450. The instructions for setting process conditions for aCFD process phase may be included in a corresponding CFD recipe phase.In some embodiments, the CFD recipe phases may be sequentially arranged,so that all instructions for a CFD process phase are executedconcurrently with that process phase.

Other computer software and/or programs stored on mass storage device2454 and/or memory device 2456 associated with system controller 2450may be employed in some embodiments. Examples of programs or sections ofprograms for this purpose include a substrate positioning program, aprocess gas control program, a pressure control program, a heatercontrol program, and a plasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto pedestal 2418and to control the spacing between the substrate and other parts ofprocess tool 2400.

A process gas control program may include code for controlling gascomposition and flow rates and optionally for flowing gas into one ormore process stations prior to deposition in order to stabilize thepressure in the process station. A pressure control program may includecode for controlling the pressure in the process station by regulating,for example, a throttle valve in the exhaust system of the processstation, a gas flow into the process station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations.

In some embodiments, there may be a user interface associated withsystem controller 2450. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 2450 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), pressure, temperature, etc. Theseparameters may be provided to the user in the form of a recipe, whichmay be entered utilizing the user interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 2450 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 2400.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 2450 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RF biaspower level, pressure, temperature, etc. The instructions may controlthe parameters to operate in-situ deposition of film stacks according tovarious embodiments described herein.

The system controller will typically include one or more memory devicesand one or more processors configured to execute the instructions sothat the apparatus will perform a method in accordance with the presentinvention. Machine-readable media containing instructions forcontrolling process operations in accordance with the present inventionmay be coupled to the system controller.

Patterning Method/Apparatus:

The apparatus/process described herein may be used in conjunction withlithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallycomprises some or all of the following steps, each step enabled with anumber of possible tools: (1) application of photoresist on a workpiece,i.e., substrate, using a spin-on or spray-on tool; (2) curing ofphotoresist using a hot plate or furnace or UV curing tool; (3) exposingthe photoresist to visible or UV or x-ray light with a tool such as awafer stepper; (4) developing the resist so as to selectively removeresist and thereby pattern it using a tool such as a wet bench; (5)transferring the resist pattern into an underlying film or workpiece byusing a dry or plasma-assisted etching tool; and (6) removing the resistusing a tool such as an RF or microwave plasma resist stripper. In oneembodiment, a SiN film is formed using a method as described herein. TheSiN film is used, for example, for one of the purposes described herein.Further, the method includes one or more steps (1)-(6) described above.

EXAMPLES

The invention is further understood by reference to the followingexamples, which are intended to be purely exemplary. The presentinvention is not limited in scope by the exemplified embodiments, whichare intended as illustrations of single aspects of the invention only.Any methods that are functionally equivalent are within the scope of theinvention. Various modifications of the invention in addition to thosedescribed herein will become apparent to those skilled in the art fromthe foregoing description and accompanying figures. Moreover, suchmodifications fall within the scope of the appended claims.

Example 1

Table 1 includes a number of reaction partners, and temperature andpressure parameters that may be used to make SiN films in accordancewith the embodiments described herein.

TABLE 1 Reactant A Reactant B Reactant C Temp(° C.) Press. (torr) Ref.index BTBAS NH₃ — 50-550 1-4 1.80-2.05 BTBAS — N₂/H₂ 50-550 1-41.80-2.05 BTBAS NH₃ N₂/H₂ 50-550 1-4 1.80-2.05 SiH₃Cl NH₃ Optionally50-550 1-4 N₂/H₂ SiH₃Cl TBA Optionally N₂/H₂ SiH₂Cl₂ NH₃ Optionally50-550 1-4 1.80-2.05 N₂/H₂ SiH₂Cl₂ TBA Optionally N₂/H₂SiH(CH₃)—(N(CH₃)₂)₂ NH₃ Optionally 50-550 1-4 1.80-2.05 N₂/H₂SiH(CH₃)(Cl₂) NH₃ Optionally 50-550 1-4 1.80-2.05 N₂/H₂ SiHCl—(N(CH₃)₂)₂NH₃ Optionally 50-550 1-4 1.80-2.05 N₂/H₂ (Si(CH₃)₂NH)₃ NH₃ Optionally50-550 1-4 1.80-2.05 N₂/H₂

Example 2

A 300 mm wafer is placed into vacuum chamber and the chamber evacuatedto 0.5 torr. The wafer is supported within the chamber on an aluminumpedestal which is heated throughout the procedure. For example, thepedestal is heated at a constant temperature that is between about 50°C. and about 550° C. The pressure in the chamber is increased to 2 torrusing an inert gas such as argon or nitrogen. Dichlorosilane (DCS) isintroduced into the reactor as a vapor phase flow at between about 1 slmand about 5 slm (standard liters per minute) for between about 1 secondand about 30 seconds in order to adsorb DCS onto the surface of thewafer. After the DCS flow is ceased, the inert gas flow in the reactorpurges the remaining vapor phase DCS and any byproducts. Then, at-butylamine (TBA) vapor phase flow is established in the reactor atbetween about 1 slm and about 5 slm for between about 1 second and about30 seconds. A plasma, for example 13.56 MHz at 2.5 kW power, is ignitedabove the wafer for between about 1 second and about 15 seconds. Theinert gas flow in the reactor purges the remaining vapor phase TBA andany byproducts. The DCS flow, inert gas purge, TBA flow, plasma andinert gas purge are repeated to deposit a SiN film of desired thickness.Each cycle as described deposits between about 0.5 Å and about 1.5 Å ofa SiN film.

Alternatively, in a CFD run, the TBA flow is run continuously. In theseruns, the same conditions as described above are used, except the TBAflow is established first and maintained. The DCS flow is introducedinto the reactor at the same rate and time as described above, followedby an inert gas purge as described above. The plasma is ignited asdescribed above, followed by an inert gas purge as described above. TheDCS flow, inert gas purge, plasma ignition and inert gas purge arerepeated to deposit a SiN film of desired thickness. Each cycle asdescribed deposits between about 0.5 Å and about 1.5 Å of a SiN film.

The SiN films produced have the following characteristics:

-   -   Non-Uniformity 3%-5% (max-min/average)    -   Non-uniformity <1% (1 s)    -   Refractive Index 1.8-1.9    -   Film stress: +20 MPa to −180 MPa    -   Dielectric constant: 5.5-6.5    -   Wet etch ratio 0.1-1.0 (to thermal oxide)

Although the foregoing has been described in some detail for purposes ofclarity of understanding, it will be apparent that certain changes andmodifications may be practiced within the scope of the appended claims.It should be noted that there are many alternative ways of implementingthe processes, systems and apparatus described. Accordingly, thedescribed embodiments are to be considered as illustrative and notrestrictive.

1. A method of forming a silicon nitride material on a substrate,comprising: (a) providing the substrate in a reaction chamber; (b)continuously exposing the substrate to a vapor phase flow of anitrogen-containing reactant wherein the nitrogen-containing reactant isadsorbed onto the surface of the substrate; (c) periodically exposingthe substrate to a vapor phase flow of a silicon-containing reactantwherein the silicon-containing reactant is adsorbed onto the surface ofthe substrate; and (d) periodically igniting a plasma in the reactionchamber when the vapor phase flow of the silicon-containing reactant hasceased.
 2. The method of claim 1, further comprising continuouslyflowing a carrier gas through the reaction chamber.
 3. The method ofclaim 1 or 2, further comprising purging to remove unabsorbedsilicon-containing reactant after (c) but before (d).
 4. The method ofclaim 1, wherein the substrate is a semiconductor wafer.
 5. The methodof claim 4, further comprising repeating (b) through (d) to form aconformal layer on the semiconductor wafer between about 1 nm and about100 nm thick.
 6. The method of claim 1, wherein the silicon-containingreactant is selected from the group consisting of a silane, a halosilaneand an aminosilane, and mixtures thereof.
 7. The method of claim 1,wherein the nitrogen-containing reactant is selected from the groupconsisting of ammonia, a hydrazine, an amine and mixtures thereof. 8.The method of claim 7, wherein the nitrogen-containing reactantcomprises a C₁₋₁₀alkyl amine.
 9. The method of claim 8, wherein theC₁₋₁₀ alkyl amine is tert-butyl amine.
 10. The method of claim 8,wherein the silicon-containing reactant is a monochlorosilane or adichlorosilane.
 11. The method of claim 4, wherein the semi-conductorwafer is heated to between about 50° C. and about 550° C.
 12. A methodof forming a silicon nitride material on a substrate, comprising: (a)forming a silicon nitride film on the substrate, said formationcomprising: (i) providing the substrate in a reaction chamber; (ii)exposing the substrate to a silicon-containing reactant in the vaporphase so that the silicon-containing reactant is adsorbed onto thesurface of the substrate; (iii) exposing the substrate to anitrogen-containing reactant in the vapor phase so that thenitrogen-containing reactant is adsorbed onto the surface of thesubstrate; (iv) igniting a plasma while the nitrogen-containing reactantis present in the vapor phase; and then, (b) exposing the siliconnitride film to a hydrogen containing plasma to remove at least somecarbon content of the silicon nitride film.
 13. The method of claim 12,wherein the substrate is a semiconductor wafer.
 14. The method of claim12, wherein (ii) is performed prior to (iii).
 15. The method of claim12, wherein (iii) is performed prior to (ii).
 16. The method of claim13, wherein (a) is repeated two or more times prior to (b).
 17. Themethod of claim 13, further comprising repeating (a) and (b) to form aconformal layer on the semiconductor wafer between about 1 nm and about100 nm thick.
 18. The method of claim 12, wherein the silicon-containingreactant is selected from the group consisting of a silane, a halosilaneand an aminosilane, and mixtures thereof.
 19. The method of claim 12,wherein the nitrogen-containing reactant comprises a C₁₋₁₀alkyl amine.20. The method of claim 18, wherein the silicon-containing reactant is achlorosilane.
 21. The method of claim 12, further comprisingcontinuously flowing a carrier gas through the reaction chamber after(i).
 22. The method of claim 13, wherein the semi-conductor wafer isheated to between about 50° C. and about 550° C.
 23. A method of forminga silicon nitride material on a substrate, comprising: (a) providing thesubstrate in a reaction chamber; (b) providing a carrier gas flowthrough the reaction chamber; (c) exposing the substrate to a vaporphase flow of a nitrogen-containing reactant wherein thenitrogen-containing reactant is adsorbed onto the surface of thesubstrate and then purging the reaction chamber; (d) exposing thesubstrate to a vapor phase flow of a silicon-containing reactant whereinthe silicon-containing reactant is adsorbed onto the surface of thesubstrate; (e) igniting a plasma in the reaction chamber after the vaporphase flow of the silicon-containing reactant has ceased; and (f)heating the substrate to between about 200° C. and about 550° C.;wherein at least one of the nitrogen-containing reactant and thesilicon-containing reactant bears one or more of a thermally removablegroup, wherein said thermally removable group decomposes at betweenabout 200° C. and about 550° C.
 24. The method of claim 23, wherein thethermally removable group is according to Formula II:

wherein each of R¹, R² and R³ is, independent of the others, H or C₁₋₃alkyl; or two of R¹, R² and R³, together with the carbon atom to whichthey are attached form form a C₃₋₇ cycloalkyl and the other of R¹, R²and R³ is H or C₁₋₃ alkyl; and wherein each of said thermally removablegroup, when part of the nitrogen-containing reactant, is attached to anitrogen or an oxygen of the nitrogen-containing reactant, and, whenpart of the silicon-containing reactant, is attached to a silicon or anitrogen or an oxygen of the silicon-containing reactant.
 25. The methodof claim 23, wherein the substrate is a semiconductor wafer.
 26. Themethod of claim 25, further comprising repeating (b) through (e) to forma conformal layer on the semiconductor wafer between about 1 nm andabout 100 nm thick.
 27. The method of claim 23, wherein (f) is performedthroughout (b) through (e).
 28. The method of claim 23, wherein thesilicon-containing reactant is selected from the group consisting of asilane, a halosilane and an aminosilane, and mixtures thereof.
 29. Themethod of claim 23, wherein the nitrogen-containing reactant is selectedfrom the group consisting of ammonia, a hydrazine, an amine and mixturesthereof.
 30. The method of claim 29, wherein the nitrogen-containingreactant is a C₁₋₁₀ alkyl amine according to formula I:

wherein each of R¹, R² and R³ is, independent of the others, H or C₁₋₃alkyl; or two of R¹, R² and R³, together with the carbon atom to whichthey are attached form form a C₃₋₇ cycloalkyl and the other of R¹, R²and R³ is H or C₁₋₃ alkyl.
 31. The method of claim 30, wherein the C₁₋₁₀alkyl amine is selected from the group consisting of isopropylamine,cyclopropylamine, sec-butylamine, tert-butyl amine, cyclobutylamine,isoamylamine, 2-methylbutan-2-amine and thexylamine.
 32. The method ofclaim 31, wherein the C₁₋₁₀ alkyl amine is tert-butyl amine.
 33. Themethod of claim 29, wherein the silicon-containing reactant is achlorosilane.
 34. The method of claim 32, wherein the semi-conductorwafer is heated to between about 450° C. and about 500° C.
 35. Anapparatus for depositing a silicon nitride film on a semiconductorwafer, the apparatus comprising: (a) a reaction chamber; (b) a source ofactivation energy to form the silicon nitride film; (c) a reactantinlet; and (d) a controller comprising instructions for: continuouslyflowing a nitrogen-containing reactant into the reaction chamber duringa deposition cycle; periodically flowing a silicon-containing reactantinto the reaction chamber during the deposition cycle; periodicallyigniting a plasma in the reaction chamber when the flow of thesilicon-containing reactant has ceased.
 36. The apparatus of claim 35,wherein the source of activation energy is a plasma generator.
 37. Theapparatus of claim 35, further including a vacuum port.
 38. Theapparatus of claim 36, wherein the plasma generator comprises inductioncoils and/or a microwave source.
 39. An apparatus for depositing asilicon nitride film on a semiconductor wafer, the apparatus comprising:(a) a reaction chamber; (b) a source of activation energy to form thesilicon nitride film; (c) a reactant inlet; and (d) a controllercomprising instructions for: flowing a nitrogen-containing reactant intothe reaction chamber during a deposition cycle; flowing asilicon-containing reactant into the reaction chamber during thedeposition cycle; periodically igniting a plasma in the reaction chamberwhen the flow of the silicon-containing reactant has ceased and whilethe nitrogen-containing reactant is present in the vapor phase in thereaction chamber.
 40. The apparatus of claim 39, wherein the source ofactivation energy is a plasma generator.
 41. The apparatus of claim 39,further including a vacuum port.
 42. The apparatus of claim 40, whereinthe plasma generator comprises induction coils and/or a microwavesource.